Cocos2D - moving sprite deformed, flickering

this occurs in both the simulator and the device. I have a sprite that is moving, its position being updated base on the physics of the game. The side in the direction of movement appears faded/slightly squished. Is there anything I can do to eliminate this effect? There's also a shimmering effect on the device, where the black edges of the sprite appear to flicker against the mostly white background.